When watching The Martian, it seems self-evident that the potato plants did not survive being frozen – but what made the soil infertile?
Soil freezes around the Arctic Circle every winter but plants still grow after the thaw. The roof was still there, so radiation doesn't seem to be the answer, either. He got the bacteria in the soil from raiding the feces collected from the other astronauts; over time, he could repeat this trick using only his own feces.